what head gasket did you use as a replacement?
also, did you properly torque it in sequesnce? there is a certain pattern to do it in......
and, did you check that the block was square before putting the head back on.....
did oyu take the head to a reliable machine shop? or some dude i na van?
you most likely wot be able to see a crack in aluminum.... you might want to just get a new tchain cover to eliminate that as an possible problem